How many 120 rolls with 1l Ilford ID-11?

[AdeoMikelo]

Hello there,

I'm reading manual for Ilford ID-11 developer and wonder how much Ilford HP5+ 400 speed 120 rolls can I process with 1l solution.
I'll be using Paterson development tank with 120 spiral, which takes 600ml.

1. First option is not to dilute (stock). After developing the first film increase the development time 10% for each successive film. I'll pour back used fluid to the stock solution, mix it and then continue development. This way I can process 10 rolls.

2. Second option is to dilute 1+3 so I'll get 4l. This is one-shot solution, so I have to divide 4l by 600ml and it'll give me full 6 tanks to develop. This way I can process only 6 rolls (and I'm left with 400ml).

If I'm thinking correctly with 35mm roll (which takes 300ml in Paterson) the second option will give 13 rolls. But shouldn't 35 be equal to 120 in terms of emulsion to develop?

Are my calculations right, or am I missing something?

 

[Dave442]

I would usually dilute and do the "one-shot" use. Generally as I'm not developing enough film to reach consistent results with replenishing used film developer. I would be more interested in trying a few different dilutions and development times. I would probably go with 1+1 dilution just for the shorter development time. I would look at how many rolls I have and make sure I have enough stock solution mixed up ahead of time.

Also, I think that the option of going with stock solution and reusing would work better with a stock solution of a larger volume than just 1 liter, so the used solution is a smaller percent of the total.

 

[chris]

If I'm thinking correctly with 35mm roll (which takes 300ml in Paterson) the second option will give 13 rolls. But shouldn't 35 be equal to 120 in terms of emulsion to develop?

You are quite right, 120 is more or less equivalent to 35 mm as far as surface area goes, but you need more developer for 120 because you need to cover it when it is in the tank. I suppose that you could just put 300 ml in the tank for a 120 and constantly invert the tank but it may give uneven development and it is probably not worth the cost saving if using on a one-shot basis.